How can doctors tell if an adrenal tumor is benign or malignant?

Size and feature. Tumors > 6 CM are high risk for malignancy. Tumors 4-6 CM are in the gray zone (you need to look at other fearues as well). Tumors < 4 CM are less likely to be malignant. There are features on the imaging studies that can also help your physcian determine the likelihood of tumor malignancy potential (hounsfield units, contrast wash out...).
Clinical picture. I agree with dr orr. A cancerous adrenal tumor looks different, and it will act differently (grows rapidly or produce excessive amounts of hormones). If these features are present, your dr may rec eval by a surgeon for removal- a pathologist can tell you if it was cancer after looking at the surgical specimen.
Most are benign. Fortunately most adrenal tumors are benign. Work-up for adrenal tumors includes hormone checks to see if the trumor is producing abnormal amounts of hormones, the size of the tumor (less than 4 CM is almost always ok) and radiographic characteristics. Needle biopsies of adrenal masses are rarely helpful unless they are used to rule out metastases (from lung cancer, etc.).

Related Questions

I was diagnosed with an adrenal tumor. My doctor says it's benign, but I'm having a lot of pain. Should I be worried?

???cause of pain??? Most non-functioning adrenal tumors that are less than 4 CM in size can be safely watched due to the low probability that they are malignant. Assuming that your tumor is that small, it would be highly unusual for the tumor to be causing any pain. I recommend that you seek out your physician's opinion what may be causing your pain. Read more...
Location. Most adrenal nodules are of benign nature and remain stable and non functioning, however they should be monitored on an interval based on size and location. Although you did not describe the nature and location of pain, you will need to discuss this further with your physician. Adrenal neoplasms can be dynamic and there is many cases reports of non secretory nodules becoming hornonally active. Read more...